Cannot be done modifying the plugin. But you could put something like this in the title of an image:
<a href="https://twitter.com/share" class="twitter-share-button" data-count="none" data-url="https://theurl.to/your/image.jpg" >Tweet</a> <iframe src="//www.facebook.com/plugins/like.php?href=https://theurl.to/your/image.jpg&layout=button_count&show_faces=true&width=500&action=like&font&colorscheme=light&height=23" scrolling="no" frameborder="0" style="border:none; overflow:hidden; width:110px; height:23px;" allowTransparency="true"></iframe>
Where, in both cases, you change the part https://theurl.to/your/image.jpg to the real URL to the full size image in question.
But you’ll have to do this manually for each image link…
